The laryngeal mask airway

The laryngeal mask airway (Fig 3) consists of an inflating oval cuff that sits obliquely over the laryngeal inlet, lying from the base of the tongue anteriorly to the upper esophagus posteriorly. Arising proximally from this is a wide-bore tube which protrudes from the mouth and can be connected to standard airway circuitry. While it is not an alternative to tracheal intubation, the laryngeal mask airway provides a clear and secure airway through which gentle positive-pressure ventilation can be applied. Although airway protection is not guaranteed, pulmonary aspiration is very uncommon. It is relatively easy to insert with minimal training or equipment. Moreover, the laryngeal mask airway may be a satisfactory or even lifesaving alternative if tracheal intubation is difficult or potentially hazardous. The laryngeal mask airway is made in a variety of sizes to accommodate all patients from the neonate to the large adult (Table.!).

Fig. 3 The laryngeal mask airway.

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Table 1 Sizing of the laryngeal mask airway

Table 1 Sizing of the laryngeal mask airway

Rejection, straining, coughing, and laryngeal spasm may occur in patients with active reflexes. Incorrect placement and obstruction may result from folding of the tip of the cuff, folding down of the epiglottis at insertion, or rotation of the laryngeal mask airway. These can usually be corrected by careful reinsertion of the laryngeal mask airway using the manufacturer's recommended technique. Persistent leakage around the cuff may be due to incorrect insertion techniques or the use of an incorrectly sized laryngeal mask airway, inadequate cuff inflation, or excessive lung inflation pressure (which should not exceed 20 cmH 2O).

The laryngeal mask airway can also be used to facilitate difficult tracheal intubation. The pharyngotracheal lumen airway

In unconscious patients with absent glossopharyngeal and laryngeal reflexes the pharyngotracheal lumen airway can be used to provide an airway which may give protection from pulmonary aspiration similar to the laryngeal mask airway. It is introduced blindly into the mouth and consists of two tubes: the longer tube passes into the upper esophagus where its cuff is inflated to protect the laryngeal inlet against regurgitated gastric contents, while the shorter tube lies with its tip above the glottic opening where its large cuff obliterates the hypopharynx. Ventilation is through the short tube, allowing a separate gastric tube to be passed through the longer tube. If the long tube enters the trachea, it can then be used as an orotracheal tube. It is relatively difficult to introduce but is an alternative if tracheal intubation is difficult or precluded.

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